1. Field of the Invention
The present invention relates to soldering irons, and in particular, to pen type soldering irons of the type having a heater assembly in which exchangeable soldering tips are mountable and which, itself, is replaceable. The invention is especially directed to such soldering irons as are used for performing soldering on printed circuit boards.
2. Description of Related Art
Typically, the heater assembly of a soldering iron of the type to which the present invention is directed has a heater assembly which includes an electrical heating element and a temperature sensor which are disposed within a tip-mounting housing. The electrical heating element and temperature sensor are electrically connected to a five wire electrical cable which runs through a handle portion of the soldering iron. For work on circuit boards sensitive to electrostatic discharge (ESD) damage, such soldering irons are generally required to have their exposed surfaces constructed of static dissipative material in order to minimize or eliminate the possibility of a potentially damaging static charge from building up thereon.
In the case of the Weller EC1503A soldering iron, sold by the Well Division of Cooper Industries, Cheraw, S.C., detachable electrical connections between exposed portions of the wires of the electrical cable and wires of the heater assembly are provided by plug and socket type, quick connect and disconnect, electrical connectors. To shield the electrical connections from each other to prevent shorting, a plastic tubing section is placed over each electrical connection. Furthermore, since the electrical cable passes through the handle with clearance (to permit the cable to move freely therethrough whenever the heater unit is pulled forward to provide access to the electrical connections or the electrical connections are pushed into the handle assembly when the heater assembly is mounted on the handle) to provide strain relief and to prevent an unintended disconnection of one of the electrical wires due to the electrical cable being pulled or otherwise subjected to tension forces rearwardly of the handle, an inner end portion of the electrical cable has clip members attached thereon. These clip members engage directly in clip-receiving apertures formed in the body of the heater assembly so as to cause tensile forces applied to the cable to bypass the electrical connections wires and be transferred from the cable to the body of the heater assembly. However, such a construction is cumbersome to assemble and because the heater assembly mounts directly to the handle, the handle must be constructed of a high temperature resistant, static dissipative material, and such materials are relatively expensive in comparison to static dissipative materials which are not high temperature resistant and are especially so as compared to nondissipative materials.
In U.S. Pat. No. 4,463,247 to Lawrence et al., a soldering iron is disclosed in which the heater unit is provided with a light bulb type base, so that it can be connected and disconnected with the handle by being screwed into and out of a threaded electrical socket in the handle. However, such a light bulb type arrangement is impractical where more than two electrical connections need to be made.
Similarly, U.S. Pat. Nos. 4,086,465 (Sylvester) and 4,431,903 (Riccio) disclose soldering irons wherein the heater assembly is electrically connected and disconnected with an electrical cord fixed in the handle by dual prong-type contacts on the heater assembly being plugged into electrical sockets hard-wired onto the electrical cord. A similar arrangement, but having a three prong electrical connection, can be found in the Weller EC1201P soldering iron. The Sylvester and Riccio soldering irons have no temperature sensor and in the Weller EC1201P soldering iron, a temperature sensing probe is provided, but is separately soldered to the electrical cable and extends through the electrical connector of the handle into the heater assembly. However, this complicates assembly of the soldering iron and precludes replacement of the sensor as a unit with the heater assembly, and should it fail, the entire soldering iron must be taken apart to replace it. On the other hand, anchoring of the electrical cable in the handle of the soldering iron, in the manner used in any of these three prior art devices, would be unsuitable with an arrangement of the type used in the initially-mentioned Weller EC1503A soldering iron.